On Dec 15, 2010, at 4:28 AM, Steve Block wrote: > I have a question about whether WebCore code makes assumptions about > the atomicity of certain read/write operations. > > The particular instance I'm interested in is IconDatabase, where > m_threadTerminationRequested is written to from the main thread (in > close() for example) and read from the DB thread (in > syncThreadMainLoop()) without any locking. It looks like the code is > written such that there's no particular synchronization requirement in > terms of the order in which the value is set and read. But there's a > risk of a garbled read in the case of a simultaneous read and write > from the two threads. > > I assume that the lack of locking is an intentional decision, based on > the fact that on all relevant architectures, a boolean read/write is > atomic?
Correct - or, at least, at the time it was correct. Have you discovered a relevant architecture where it is no longer correct? > Is this a general WebCore policy? It would be great if somebody could > confirm this, or point out why I'm wrong. I wouldn't be surprised if there were other examples of an unprotected thread shared boolean in either WebCore or any platform's WebKit. I *would* be surprised if there was an example of *any other data type* that was shared between threads unprotected. That said, I don't think we have any general WebCore policies about multithread practices. There might be value in such a document. ~Brady > > Thanks, > Steve > > -- > Google UK Limited > Registered Office: Belgrave House, 76 Buckingham Palace Road, London SW1W 9TQ > Registered in England Number: 3977902 _______________________________________________ webkit-dev mailing list [email protected] http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
